Control switching system for automatic exposure timers



Sept. 23, 1952 LEE 2,611,809

CONTROL SWITCHING SYSTEM FOR AUTOMATIC EXPOSURE TIMERS Original Filed 00th 9, 1946 2 SHEETS-SHEET 1 2% FIGURE I FIGURE 3 INVENTOR. H. E

Sept. 23, 1952 R. H. LEE 2,611,809

CONTROL SWITCHING SYSTEM FOR AUTOMATIC EXPOSURE TIMERS Original Filed Oct. 9, 1946 2 SHEETS-SHEET 2 FIGURE41 INVENTOR. R0 ERT H. LEE

ATTY.

Patented Sept. 23, 1952 UNITED STATES PATENT OFFlCE CONTROL. SWITCHING SYSTEM FOR AUTO- MATIC EXPOSURE TIMERS Robert H. Lee, Indianapolis, Ind, assignor, by

I mesne assignments, to Micro Recording I pany, a-corporation of Florida Com- Original application October 9, 1946, Serial No. 702,124. "Divided and this application July 5, 1947, Serial No. 759,205

My invention relates to improvements in means for electromagnetically operating a plurality of switches, which are adapted for successive operation.

It is one of the objects of my invention to provide means for controlling the successive operation of a plurality of electromagnetically operated switches as to cause said switchesto operate in a predetermined sequence.

A further object of my invention is the pro-- vision of a plurality of magneticallyoperated switches adapted for successiveoperation and the control of said successive operation through the operation of a plurality of tubes, each including a cathode, an anode and a grid, said tubes being so arranged and connected as tobe successively energized to control the energization of the electromagnetically operated switches and the operation of said tubes being controlled by light controlling means, which'in turn controls the time elapsing between the successiveopera tion of the switches.

A further object of my invention isto provide a plurality of magnetically 'operatedswitches which are adapted for successive operation and to...

provide, for controlling the successive. operation of said switches, a tube for each switch including a cathode, an anodeand a grid, the tubes being so energized as to effect successive operation of the switches.

Further objects and advantages of my invention will appear more fullyhereinafter in the appended specification and claims.

For the purpose of disclosing the invention, I

have illustrated an embodiment thereof, in the accompanying drawings, in which: I,

Fig. 1 is an end elevation (more or lessdia grammatic) of a microfilm camera and its control mechanism;

Fig. 2 is a longitudinal, section view (more or lessdiagrammatic) of theoperating mechanism of the camera;

Fig. 3 is an end mechanism for the camera shutter;

s Fig. 4' is a diagrammatic view of the'circuit ar rangement of the timingcontrol mechanism" In the embodiment illustrated, having par ticular reference to Figs. 1 to 4,1 provide amicrofilm camera I suitably supported above the 010-- ject 2 and alongside the-camera,- I'preferably mount the timing control mechanism 3 so that the light reflected from theobject'beneaththe camera to the timing control willbe substantially the same as, if not identical with,'that reflected into the lens of the camera. This timing conelevation ofthey operating 12 Claims. (Cl. 175-321) trol includes a casing having a small opening in its'bott'om through which the light reflected from the object is adapted to pass to influence the elec tric eye forming a part of the timing control.

The circuit diagram for the timing control mechanism 3 is shown in'Figure 4. For the purpose of providing suitable illumination for the object' I preferably provide on each side of the camera illuminating lamps 4 having associated therewith suitable reflectors 5.

The camera I is provided with asuitable lens 6 through which the rays of light pass to impinge upon a film negative mounted within the camera. The admission of light through the lens and onto the negative is controlled by a shutter l pivoted to'swing on a pivot support or shaft 8. This shutter l is adapted to be opened and closed through the medium of suitable electromagnets 9 and I0 between which is mounted an armature 1! carried on a suitable shaft I2, provided with an arm 13 having a rack l4 meshing with a pinion limountedon the shaft 8 carrying the shutter so that as the shaft is rotated in one direction or theother, the shutterwill be opened or closed.

The negative film is adapted to be wound from a supply spool It onto a receiving spool ll. These respective spools are driven by suitable belt drives 18 and I9 from a puIleyZB of an electric motor 2|. controlled by a switch including a switch arm 22 and a relatively stationary contact 23., The switch arm 22 is biased in'an open position by suitable coil spring 24 and is carried by an arm 25 pivoted at 26. "This arm 25 is moved in one direction against the bias of the spring 24 through the mediumof an-electromagnet 21. The lower end of the arm isadapted to ride on a cam 28 carried on the shaft of the reel 11, which cam hasa low spot 28a into which the end of the arm 25 is adapted to drop when the switch arm 25 is in its open position.

In Fig. 4, I have illustrated a diagrammatic view of a circuit arrangement of the various control elements and their circuit relation with one another, for controlling the operation of the different components of the camera.- In the cir cuit arrangement shown, the two leads 31' and 38 which are adapted to be connected with any suitable alternating current supply, in the specific case-a 115 volt alternating current supply, are connected to the opposite terminals of the primary'winding 39' of a transformer Mi through suitable fuses and through a suitable manually operated control switch 4!. A secondary wind-- The circuit of this electric motor is furnish, in the embodiment illustrated, 150 voltdirect current power through neutral conductor 48' and positive conductor 5| to the plate circuits;

of the gas triodes or tubes 45, 46 and 41, and the double rectifier also suppliesnegativebias (150 volt direct current) through negative conductor 52 and neutral conductor 48' for control of the,

grids on the triode tubes 45, 46 and 41. A winding 53 of the transformer 40-supplies filament.

power to a rectifier tube 54and a winding 55 ofthe transformer 40 supplies alternating current voltage to the rectifier tube 54, which supplies.

through conductor 55 direct current plate power to .a.tube 55-which isconnected in series with a tube 56,.

conductor5l. Thecondens'ers58, 59 and 60 are. forlthepurpose of filtering the three. direct current output voltages, the condenser 58. being.

connected. across the conductors48' and 5| and the condenser 59' being. connected across the conductors 48. and 52 while the condenser 60' is connected across .the. conductors .55? and .51..

An exposure cycle is initiated through the.

momentary. closure of. the. manually. operated switch.5 8..which completes the circuit fromv the lead or.-conductor.59,through'.the coil 60 of a. relay controlling. switches; GI and 62, through switch 63;-back to.lead64. Hereafter reference will be. made to .the switches. controlledby the relaysghaving coils 60, 69-.and--8 9.- One position of .these .switches will I be .referred-to as the op-- erated position and they other position of the switches,will-bereferred to as the released .po-

sition f Theiterm operated position is usedto indicate the positionof the switches when they. are.,-moved=from the.position-illustrated in the.

drawingsdownwardly, under the influence'of the relays having the coils sc, 6$and 89-;and--the term released position isnsedto indicate their normal or biased-position, that is, the position illustrated in the drawings Withtheswitch 62 in closed position, thecircuit-,-from the alternating current power source qf h n q enp 1 ispQmPlete -by Y f n tor; 65 through the switches GLand-Gland by the return ,conductor ,6Q,;-.th us energizing solenoid 0 h sfl ensshutt r. -1 the am n an switch; it also closes, the: circuit 1 between 'the positive, lead Q; vo lt 1 direct --current with respect to conductor-481:)- through theresistor Bl to furnish positive bias on the grid 68 0f v, the tube-. 51. e. ube. 5...; be mes pe ati and energizes the coil ,69;-;.of gthe electromagnet controlling the relay switcheslfl and H to effect operation of these switches, and tube. 45 ,;being a gaseous triode, remainsoperativeuntil its plate voltageis' reduced {at a .later point in the ,cycle. The.operati0n of thewrelayswitch ll initiates no action, since itisdntseries ,With, the lowelf contact of switch '63 ;wh ichghas not yet been; closed:

Switch- !0 in mqving from its normal position disconnects the negative lead 52% 150-.voltdirect currentwith-respect to conductor 48/) from the grid 12- of. the gas triodetube A6,; and also removes a short-circuit 1 from around condenser 13gwhich then beccmescharged from.: the timer circuit through;conductors;13 andl3b as will be described in, more detail hereinafter. A

The.- current return is. through the I come sufficiently built up, it effects the closure 4 momentary closure of switch 58 is sufficient to start the cycle because tube 45 becomes operative by a momentary closure of switch contact GI and the shutter 1 remains open until winding 9 -is energized.

The timer control amplifier; circuit including tubes 56 and 56' supplies current to the condenser 13 allowing a charge to build up in this condenser 13. The operation of this circuit will be explained later. When this charge has beof the camera shutter 1, through the operation of the tube 46, thusshutting off the exposure of the negative. Accordingly, the time it takes for thecharge in the condenser 13 determines the length ofxtime of the camera exposure and this build-up time'is controlled by an electric eye tube 14 which is subjected to the light reflected from the image and is therefore responsive to the variations in said light. As has heretofore been explained, the; timer is arranged in the timercasingfiflisposed beside the camera I. The

electric eyell and its associated timing elements for charging condenser 13 are mounted in the casing} with the electric eye in such a position relative tO-a, small opening in the bottom of the casingas tov receive the light'refiected from-the objectto be photographed, inthe same manner as the camera lens receives. the. light. This is more particularly illustrated in Fig. 1; The photoelectric eye Misconnectedin an amplifier circuit including tubes 56 vand5li? which amplifies thelcurrent producedin the eye, resulting from thelight. falling on the. screen of the eye, to a valuesufficiently high to control the build-up of :the charge in the condenser 13.

In this :.timer controlcircuit for charging condenser..13,. two voltage control'or regulator tubes 15-and.16;.are connected in series with a resistor 11 across the conductors 55.1 and51, and supply constant voltageto the amplifying circuit. The photoelectric tube 14 is connected between the positive. terminal 18 ofthe regulator tube 16 andithe control grid 'lfl ofthe amplifier tube 55'. The (control-grid 79-of this amplifier tube 56- is connected: to conductor-51 through a resistor 80 of :a value sufficient-to create-suitable variations in the voltage of thegrid resulting from current fiow irom the photoelectric tube 14. Thecath- .ode 8| of the amplifier tube 56' is connected to conductor 51 through; resistor 82; whichlimits the current flow; through the amplifier; tube; The plate of the amplifier tube 56 is connected to thecathode- -84-of'the-amplifier-tube 56;- A .resistor 82 is connectedbetween the positive terminal 18 of the regulator tube 76 and the oathodefllof the amplifier tube 56? to provide a bias of'such-value'that the current passing through the amplifier tube 56, when no light is presented to the photoelectric'eye 14; willbe nearlyzero...

terminal of condenser-J3. and also to the positive lead 555:. through conducton; 73b;

Operation of;the.photo.-cell' amplifying circuit isa gfollowsz With the camera shutter-open, the

light 1 reflected"; from; the; object energizes .,the photoelectric; eye .14, which, in accordance with he-aw. lrknowncha cmistic ofi his typ of :de-

e-.1 111? erm t zc r ent; f w :pro o o r.- o;

The grid tube 56 applied from rectifier 54 through conductor 131), through condenser 13, and through conductor 13a, attracts the electrons from the cathode 84 of the amplifier tube 56 and the electrons are accelerated and pass through the aforesaid screen grid to impinge upon the plate 86 of the amplifier tube 56. The plate gives up electrons under the bombardment and these areattracted back to the screen grid 88 of the tube 56 and pass to the negative terminal of the condenser 13, building up a voltage across the condenser 13.

- When the voltage across the condenser 13 has reached a, point sufiiciently high to start a cur-' rent flow in the gas triode 46, current flow will be established through the relay winding 69. With the relay winding 69 energized, the switch 63 is moved to operated position and with switch 1| in operated position, a circuit is established through the electromagnet 9, thus moving the camera shutter to closed position. Upon firing of tube 46, the low resistance path of this tube connects condenser I9! in shunt to tube 45 and the charge on this condenser applies a negative voltage to the plate of tube 45 to de-energize this tube, thereby deenergizing the winding and permitting switches 18 and 1| to move back to normal or open position. A time delay circuit however, is provided to allow current to flow through relay coil 69 for a period of time after current flow ceases through the tube 45 and thus, for a i short period of time, maintaining switch 1i closed I for a, sufficient length of time after the closure of the switch 63 to complete the movement of the shutter 1 to its closed position. Thus for a short interval of time the switch H controlled by the relay coil 69 and the switch 63 controlled by the relay coil 89 are both in closed position, allowing current flow from the conductor 66 through the solenoid 9, through the switch 63, through the switch 1|, through the conductor 64as above explained, maintaining the current flow through the winding 9 of the solenoid sufiiciently long to complete the closure of the shutter.

The time delay in deenergization of relay coil 69 is accomplished by means of a condenser 93 and a resistor 94 in series, being connected across the relay coil 69. After current flow has ceased through gas triode 45, the discharge current from condenser 93 through resistor 94 keeps the relay coil 69 energized. The period during which the relay coil 69 is sufiiciently energized to keep switches 19 and 1| in a closed position is dependent on the capacity of condenser 93,.the resistor 94, the resistance of relay coil 69, and the charge which was present on condenser 93 at the instant current flow through gas triode ceased. The said valuesare pre-set to get the desired amount of delay time in the releasing of switches 19 and 1|. This delay time is the time during which solenoid 9, controlling the closure of the camera shutter 1, remains energized. v

Immediately after the closing of the shutter has taken place, the relay coil 69 becomes deenergized, thereby releasing switches 10 and 1|. The switch 1| completes a circuit from the conductor 64 through the lower contact or switch 63, through the switch 1|, through the conductor 19 to the solenoid 21, which operates the switch 22 to close the circuit through the motor 2|, driving the film take-up of the camera and thus moving the film one step to present a fresh film for photographic purposes. The motor wind-up is stopped when the cam Wheel 28 permits the arm 25 of the motor control-switch to drop onto the low spot 29a of the cam wheel, thus opening the switch 22. The circuit through the solenoid 21 is also shutoff through the releasing of the switch 63 which is effected when the relay coil 89 is de-energized.

With the switch released, that is with the coil 89 deenergized and switch 95 in its up position, a short circuit will be established around the condenser 96 and accordingly, the condenser will not be receiving a charge. Duringthe time, however, when the relay coil 89 is energized, the switch 95 will be moved to its down position and as a result, the condenser 96 will be connected across the leads 5! and 52, and a-charge will be built up in the condenser, due to the potential difference between leads 5| and 52. trol grid 91, of the tube 41 is connected to the condenser 96 and when the charge of the condenser 96 has been built up to reach a sufficient positive value to trigger the control grid 91, cur-.

rent flow will be established through the tube 41. With current flowing through tube 41, the

voltage at theplate 92 of the tube 46 is lowered below its sustaining current value by means of the discharge of condenser 96 which is connected between the plate 92 of the tube 46 and the platev To further explain the action of the timercircuit, at the instant that switch 95 is caused to,

open by current flow through the relay coil 89, the circuit from the negative conductor 52 through switch 95 to the grid of gas triode 41 is opened, thus removing a short-circuit from around condenser 96. This allows a charge to build up across condenser 96, resulting from current flow through resistor llln coming from the positive conductor 5!. When the voltage across the condenser 96 has reached the critical point, it allows current flow through the gas triode 41 and through the resistor I02. Firing of tube 41 connects condenser 99 in shunt to tube 46, and this condenser applies a negative voltage to the plate of tube 46 to de-energize it. Thus, the relay coil 89 is deenergized, allowing for releasing of the switches 10 and 15. At this instant, the timer has completed its cycle and is ready for the starting of another cycle. The grid 68 of the gas triode 45, grid 12 of the gastriode 46 and the grid 91 of gas triode 41 are held at a negative potential by connections to conductor 52, which prevents start of current flow through any tube. The gas triode 41 at the end of the cycle is conducting current so that holding the grid at the negative potential does not efiect the current flow in this tube. The purpose of gas triode 41,

The con-.

resistor I02. and condenser 98' are 1 purely. to. quench the current flow. in gastriode 46;- inorder. to terminate the cycle. Thetube 41 is quenched whentube 45. is re-energized to connect condensers I01 and 98 in shunt to. the tube-41, and the charge on condenser 98. applies a negative voltage to the plate of tube 41' to de-energize this tube.

Inoperation, thecolor ofthelight sources and correspondingly, the colorof the lightreflected from the object vary under dififerent conditions of operation. For instance, a change in voltagein the input line may affect the. color characteristic or intensity of the lights. 44. In orderto compensate for this change, I provide a' means.

for controlling the linearity of the amplifying tubes 56 and 56, which consists in properly selecting the characteristic of the tubes and associating with each of the. tubes in the cathode circuit respectively resistances 82' and 85. These resistances are so selected as to cut down the response-of the tubes 56 'and 56' at low light values which efiect the tube 14'. By-this arrangement, I am enabled to compensate for the differenceinresponse to varying colorvalues between the light responsive means 74 cm theone hand and the negative on the other.

In-order to obtain the above characteristics,- in the specific embodiment of my invention illustrated, the tube 56' comprises a 6AC7 tube with the screen grid, the suppressor grid, and the plate tied together to obtain the characteristic of a sharp, cut off 'triode with the resistance 82 having a value of 2,000 ohms and a resistance 82 having the value of one megohm. Likewise, the tube 56 is a 6AC7 tube with the screen grid and the suppressor grid tied together,- andthe resistor 85 has the value of one megohm;

Summarizing, the operation of the-parts is as follows:

- Closing of switch 58 energizes relay coil 60 through upper contacts of SWitCh 63, thereby closing contacts 6| and 62.

Contact 62' operates solenoid lB -to open the shutter. Contact 6| applies positive voltage to the grid 68 of tube 45 to energize relay coilBQ which operates contacts '10 and l I.

Opening of contact l'fl removes a short-circuit around condenser 13 which begins to charge from the photocellcircuit in a direction to bias the grid 12 in a positive direction. Operation of contact "H has no efiect. As-soonas condenser 73 reaches a predetermined charge, tube Mi operates to energize relay winding 89 which operatescontacts 63 and 95' Operation of contact 63first'opensthe circuit ofrelay-coil 60 to release contacts fii and 62; and: then completes a circuitthrough its-lowencontact and through switch H to energize solenoid 9 which moves'the shutter to" closed position;

Upon firing of tube-46, the low resistance-path ofthis tube connects condenser I01 'in -shuntto' tube 45 and the charge on this condenser applies a negative voltage to the plate of tube1-45 to'deenergize this tube.

Relay coil 69 isshunted by. a delay circuit to maintain this coil energized a sufiicient time to allow the shutter to move/to completely. closed. position, and then relay contacts lfliand-H are.

released.

Release of contact-10 short-circuits.-condenser- 73- and dischargesthis condenser. Releaseof.

contact H de-energizes theshuttenclosing;sole? noid- Sand energizes magnet 21 which'closes the circuit of the film: feeding; motor ..to-; starti the motor into. operation;

Opening-of contact 95 at the timerofroperation. of relay;89;removes a short-circuit fromaround condenser. 96 andthis condenser begins'charging. through resistance lllll; After. a. predetermined timeof sufiicient duration to permittheswitch arm;25; Figure 2, to..ride.out' of the slotcin'the cam 28, condenser.96 becomes charged .to a value suflicienttocause operation of the tube 41, and this .tube applies a negative stopping .voltageto the anode. of tube. 4B.from.the charge: on condenser 98. After a short time determined by the delay circuit in shunt: to thecoil 89,-. relayfcone tacts 63 .and:95 are released, and release OLE-1001].- tact 63. opensthe. circuit of the motor starting coil 21, but the motor switch 22.23. is..maintained closed by the switcharm 25 engaging the cam 28, and the motor continues to operate until.

. the switch arm 25.drops into the slot in thecam.

Release of therelaycontacts 63 and. 95 places the circuit in condition to startanotheri cycle of operation as described above.

When tube 45.is re-energized,. the low: resistance path of this tube connects condensers. [0|

:pending application for Automatic; Exposure Timer for Cameras, Serial No. 702,124, filed October 9, 1946,.nowPatent No.2, 577,774...

I claim as my invention:

1. In combination, a pair of grid controlled gas tubes, means normally applying a negative potential to the grids of.both. tubes, time. delay. means rendered operative upon the firinguofuone tube for applying starting potentialtothe grid: of. thesecond tube, and delay-control means including a light sensitive device controlling said time delay means to vary the periodof delaywith changes in value oflight'falling on said device.

2. A combination according to claim 1 wherein said delay-control means. includes means -controlled by said light sensitive device and acting on said delay means to vary the period of delay inverselywith the intensity of: thezlightfalling on said device.

3. A combination according to claim 1 and including means rendered: operative upon energization of the-second tube to d'e-energize the first tube and toapplynegative potential to the grid of the second tube.

4. In combination,- three grid controll'edigas tubes arranged in a series, means normally applying a negative potential to the'grids of all three tubes, time. delay means rendered'operative upon thefiring of the first tube-to produce firing of the second-tube, a-second time delay means rendered operative upon firing ofthe second tube for firing the third tube, and means including a light sensitive device fo'r controlling one-of said time delay means to vary the period ofdelay with variations in the value oflight falling on said device. 7

5. A combination according'to claim Land including means controlled by the energization of each tube in said series for applying: a sup-- pressing voltage to the plate element of the -pre-- ceding tube of the series.

6. In combination a gas tube'having a cathode; a grid, and an anode,*a source of 'biasing.voltage,1 a condenser, a connection fromthe positive terminal of said source to said cathode,- acon trolling the conductance of said amplifier tube.

7. In combination, a pair of grid controlled gas tubes, a source of negative potential, connections from said source for applying negative potential to the grids of said tubes whereby said v tubes normally are inoperative, an electromagnetic relay connected in the plate circuit of one tube and having a pair of normally closed contacts connected in the biasing grid circuit of the other tube, a condenser connected in shunt to said contacts and normally being shortcircuited, and a connection from the grid of the second tube to a source of positive potential for charging the grid of the second tube positively when said relay becomes energized.

8. A combination according to claim 7 and including a light-sensitive device for controlling the rate of charge of said condenser from said source of positive potential in accordance with the value of light falling on said device.

9. In combination, three grid controlled gas tubes arranged in series, a source of negative potential, connections from said source for applying negative potential to the grids of said tubes whereby said tubes normally are inoperative, an electromagnetic relay connected in the plate circuit of each of the first and second tubes, the switch of the relay of said first tube having a pair of normally closed contacts connected in the grid biasing circuit of the second tube and the switch of the relay connected to the second tube having a pair of normally closed contacts connected in the grid biasing circuit of the third tube, a condenser connected in shunt toeach of said pairs of normally closed contacts, connections from a source of positive potential to the grids of the second and third tubes for charging said grids positively when said contacts are open, means for applying a starting potential to the grid of the first tube, and means controlled by the energization of each tube in said series for applying a suppressing voltage to the plate element of the preceding tube of the series. I

10. A combination according to claim 9 and 10 including a grid-controlled amplifier tube connected in the connection from said source of positive potential to the grid of said second tube, and a light-sensitive device controlling the conductance of said amplifier tube.

11. In combination, a pair of electromagnetically operated relays each having a normally deenergized operating circuit, time delay means rendered operative upon the operation of one of said relays for energizing the operating circuit of the other of said relays, and means including a light sensitive device controlling said time delay means to vary the period of delay with changes in value of light falling on said device.

12. A relay system comprising first and second electromagnetic relays each having a pair of normally open contacts which close upon energization of the relay, a circuit to be controlled by said relays including both pairs of said normally open contacts connected in series circuit relation therein,,means for energizing said first relay, a time delay device controlled by said first relay upon energization thereof for energizing said second relay after a predetermined time delay, and a light-sensitive device controlling said time delay device to vary the period of delay with changes in value of light influencing said light-sensitive device.

ROBERT H. LEE.

REFERENCES CITED The following references are of record in the of this patent:

UNITED STATES PATENTS Number Name Date 1,516,646 Rosely Nov. 25, 1924 1,998,950 Cockrell Apr. 23, 1935 2,104,128 Honaman et a1 Jan. 4, 1938 2,157,690 Claugh May 9, 1939 2,207,055 Goodling July 9, 1940' 2,223,163 Boeker Nov. 26, 1940 2,259,287 Bendz Oct. 14, 1941 2,274,158 Penther Feb. 24, 1942 2,370,727 Holden Mar. 6, 1945 2,414,443 Busch Jan. 21, 1947 2,422,020 Kingsmill June 20, 1947 2,433,254 Aiken Dec. 23, 1947 2,434,101 Cann Jan. 6, 1948 2,451,997 Undy Oct. 19, 1948 2,515,762 Dimmick July 18, 1950 2,538,789 Maynard Jan. 23, 1951 OTHER REFERENCES Review of Scientific Instruments, Nov. 1939, pages 323-24. 

